Additive manufacturing is still an emerging process in the aerospace industry and suffers from a particular disadvantage in that there are limited known techniques of removing the excess powder from internal cavities.
In other applications vibration finishing or peening are used. Both of these concepts use surrounding media to impact the surfaces of components to smooth or clean the surfaces. These concepts are usually used on external surfaces for solid components, for example on turbine blades following investment casting manufacture.
However, for cleaning and smoothing internal cavities and channels, the processes are more complex. A high pressure air blasting technique (using titanium powder as the abrasive agent) is used to remove the solid powder as far into the channel as possible (approximately 30-50 mm). A titanium tool is then used to manually chisel the remainder of the powder out.
Vibro-finishing involves submerging the entire powder encased component in a vibrating media, for example ball bearings or ceramic pebbles. One of the factors affecting the rate of abrasion/cleaning is the surface area available to contact the media. Certain internal channels and cavities will have a small aperture with respect to the size of the external surface area of the component in which they are formed therefore access into the channel will be limited. The erosion rate of the powder in the channel with respect to the erosion of the external surfaces will be very slow. As a result of the slow erosion rate, significant periods of time would be needed to clear the entire channel or cavity by this method. Sharp or sensitive features on the external surfaces would become rounded off and damaged if this technique was applied for long periods of time.
The current blasting and chiselling technique is also quite slow. It can take of the order of 20-30 minutes to clear a single channel or cavity in a component, and longer for larger channels or cavities. As the process has to be repeated for each channel or cavity in the component, this can add up significantly. Also, some powder remains on the walls of the channel and there is difficulty in clearing bends as a direct line of sight is required for the tool.
The manual dependency of the process results in expensive labour costs which could be avoided with a more automated solution.
The present invention aims to ameliorate or solve one or more of the above problems.